The invention relates to a device for retaining substrates as defined by the preamble of claim 1.
Such a device is used for the horizontal or vertical setting of a plurality of substrates such as wafers or substrates for the production of photovoltaic elements. The device with the substrates inside is dipped in processing baths to etch, clean or dry and then lifted out again.
Based on the prior art such devices which are also called trays or carriers usually consist of four circumferential walls. On the inside of the vis-à-vis longitudinal walls there are vertically running slits in which the substrates are inserted on the edges. The longitudinal walls can be bent inward in the area of their lower edges so that the substrates do not fall out at the bottom. Such a device is known, for instance, from U.S. Pat. No. 5,299,901. Similar devices are described in EP 0 385 536, U.S. Pat. No. 4,963,069 as well as U.S. Pat. No. 4,722,752.
A device of this type is known, for example, from DE 42 23 326 B1 as well as DE 44 28 169 C2. With this the substrates are supported on several rod-like carrier elements which connect two adjacent vis-à-vis walls with each other. These devices do not have longitudinal walls with slits.
In practical use it sometimes occurs that the hydrogen created in a caustic bath during the etching process sticks in the form of bubbles to the surface of the substrates. Because of this the substrates can be lifted out of the device and float in the caustic bath. Removal of such floating substrates requires additional effort. Undesired contaminations of the processing fluids may occur during this.
From DE 43 00 205 A1 a cassette for retaining the substrates is known. The cassette has an insert in which the substrates are supported on two carrier elements. A counter carrier element is provided to hold the substrates in place. The suggested cassette prevents the substrates from floating up in the caustic bath. The loading or unloading of the substrates is time-consuming, however. First the insert must be lifted out of the cassette and then the counter carrier element must be removed.
The object of the invention is to eliminate the drawbacks of the prior art. In particular a device is to be specified with which substrates can be prevented from floating up and which can be handled as simply as possible.